OK, let us be complete. Filling any pen it should be automatic to wipe excess ink off the nib on the bottle as you withdraw it.
In the case of piston fillers I then make three more slight movements with the piston: down a smidgin (pen over the bottle or else up-pointed), back up the same smidgin, then down half a smidgin (pointed up). Then comes the section / nib wipe I mentioned. My thinking behind those extra piston movements is to remove excess ink from the feed area, but not to leave the piston tight at the back of the barrel. The latter notion comes from something I read about Aurora 88s somewhere.
In the case of plunge fillers, having completed the fill I leave the shutoff valve closed until the ink line visibly weakens, which can take a little while. This has resolved early-blob issues for those. All forms of rubber sac pen are simply used after the cosmetic wipe.
Deep in the weeds on filling technique. I love it. And appreciate you taking the time to share.